Hydroconversion processes are important in the modern world in providing important basic fuels for everyday life. As it becomes of an increasing necessity to utilize heavier crude oil feedstocks, the oil refining industry has turned to hydrocracking processes to provide the lighter basic fuels which modern society demands. While amorphous hydrocracking catalysts are used, modern hydrocracking catalysts are often based on zeolitic materials.
Faujasite materials are one of the main zeolitic materials proposed for hydrocracking use. Early findings showed that modification of the basic materials described in U.S. Pat. No. 3,130,007 to produce a lowering of the unit cell size, gave improved selectivity to the desired middle distillate, or mid-barrel, products. To achieve this, various combinations of steam calcination and dealumination, usually acid-dealumination, techniques have been proposed.
However in certain regions, eg North America, middle distillate products are not the most desired aim of hydrocracking, instead the lighter liquid products boiling below 191° C. are more in demand. Such products are called the naphtha fractions, with heavy naphtha (the fraction boiling from 82° C. to 191° C.) being in particular more desirable. Faujasites having a unit cell size of 24.40 Å or more are known to be more naphtha-selective than those with a lower unit cell size (which are more commonly used in middle distillate-selective catalysts). For faujasites with unit cell size above 24.40 Å, it is found that the higher unit cell size, the higher the selectivity to naphtha, and to heavy naphtha in particular.